In a typical cellular system, also referred to as a wireless communications network, wireless terminals, also known as mobile stations and/or user equipment units communicate via a Radio Access Network (RAN) to one or more core networks. The wireless terminals can be M2M devices, Internet-of-Things devices, mobile stations or user equipment units such as mobile telephones also known as “cellular” telephones, and laptops with wireless capability, for example, portable, pocket, hand-held, computer-comprised, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a Radio Base Station (RBS), which in some networks is also called “NodeB” or “Bnode” or “Evolved NodeB” or “eNodeB” or “eNB” and which in this document also is referred to as a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units within range of the base stations.
In some versions of the radio access network, several base stations are typically connected, e.g., by landlines or microwave, to a Radio Network Controller (RNC). The radio network controller, also sometimes termed a Base Station Controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. Long Term Evolution (LTE) together with Evolved Packet Core (EPC) is the newest addition to the 3GPP family.
In order to transmit/receive data to/from a mobile terminal such as a UE, the UE needs to have an established RRC connection. When in RRC connected mode, the UE may operate in different communication states. In 3GPP, these communication states are referred to as RRC states. Inactivity for a certain time in a connected state, which is determined by a timer, generally results in transition to a less resource consuming state, while activity results in transition to a higher state in which more resources are required by the UE and the RAN. An example of a less resource consuming state is an idle mode and an even less resource consuming state is a sleep mode also known as power saving state. A device in a sleep mode may be employing power saving methods such as Extended long DRX in idle mode, Extended long DRX in connected mode or Power Saving Mode (PSM).